Robust process for the preparation of high chloride emulsions

Abstract

A method is disclosed of manufacturing radiation-sensitive emulsions by a pulsed flow double-jet process in which high chloride silver halide grains are grown in the presence of a thioether ripening agent in the dispersing medium in the reaction vessel the silver halide grains exhibiting an average grain roundness coefficient n in the range of from 2 to less than 15.

What is claimed is: 
     
       1. A method of manufacturing radiation-sensitive emulsions containing regular grains having six {100} crystal faces which extend to projected peripheral edges of the grain viewed normal to the {100} crystal faces, comprised of (a) creating a first population of silver halide grains in a stirred aqueous dispersing medium,   (b) producing a second population of silver halide grains in the stirred aqueous dispersing medium by simultaneously introducing a silver salt solution and a halide salt solution into the dispersing medium,   (c) while continuing stirring, simultaneously halting introduction of the silver salt solution and the halide salt solution to dissolve the second grain population, and   (d) repeating steps (b) and (c) until the first grain population has increased to a selected larger size,   WHEREIN   (1) the halide salt solution is chosen to form silver halide grains containing greater than 50 mole percent chloride, based on silver, and   (2) steps (a) through (d) are performed with a thioether ripening agent in the dispersing medium, the silver halide grains formed exhibit an average grain roundness coefficient n in the range of from 2 to less than 15,     n satisfying the formula:   x.sup.n +y.sup.n =R.sup.n     in which     R is any vector extending from the center of a {100} crystal face of a grain to the projected peripheral edge of the grain viewed normal to the {100} crystal face;   x is an X axis coordinate of R;   y is a Y axis coordinate of R; and   X and Y are mutually perpendicular axes in the plane of the {100} crystal face.   
     
     
       2. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein the grains formed contain greater than 70 mole percent chloride, based on silver. 
     
     
       3. A method of manufacturing radiation-sensitive emulsions according to claim 2 wherein the grains formed greater than 90 mole percent chloride, based on silver. 
     
     
       4. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein the grains are silver iodochloride grains containing from 0.05 to 3 mole percent iodide, based on silver. 
     
     
       5. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein the roundness coefficient n is in the range of from 4 to 15. 
     
     
       6. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein a rotatable stirring head is employed that is rotated at less than 1000 revolutions per minute. 
     
     
       7. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein successive emulsion preparations are conducted using a rotatable stirring head rotated in the range of from 700 to 1750 revolutions per minute, the revolutions per minute being changed by greater than 200 revolutions per minute from one emulsion preparation to the next while changing the roundness index n of the emulsions prepared by less than 10 percent. 
     
     
       8. A method of manufacturing radiation-sensitive emulsions according to claim 1 wherein the time t elapsed in step (a) exceeds the time T elapsed in step (b). 
     
     
       9. A method of manufacturing radiation-sensitive emulsion according to claim 1 wherein the time t elapsed in step (a) is less than 10 minutes and the time T elapsed in step (b) ranges from 30 seconds to 5 minutes. 
     
     
       10. A method of manufacturing radiation-sensitive emulsions according to claim 9 wherein time t is in the range of from 30 seconds to 8 minutes.